1. Field of the Invention
The present invention generally relates to methods and apparatus utilized in subterranean wells. More particularly, the invention relates to methods and apparatus to control fluid flow between a tubing string bore and an ambient region.
2. Description of the Related Art
Extracting hydrocarbons from subterranean formations typically involves running a tubular string into a well. Illustrative tubular strings include work strings, completion strings and production string. Some operations subsequent to (or during) running a tubular string into a wellbore, require the presence of fluid in the tubular string. To this end, it is advantageous for fluid in the wellbore to enter the tubular string as the tubular string is being lowered into the wellbore. If unrestricted fluid communication exists between the bore formed by the tubular string and the annulus formed between the tubular string and the wellbore, fluid pressure in the tubular string bore and the annulus may be equalized, thereby facilitating some operations.
In general, the tubular string bore may be filled with fluid either by flowing fluid into the bore from the wellbore surface, or by allowing fluid already in the wellbore (which is typically present after drilling) to flow into the tubular string bore via an opening in the sidewall of the tubular string. However, filling the tubular string bore with fluid from the wellbore surface is typically not desirable. Therefore, it is preferable to fill the tubular string bore with fluid from the annulus.
While the tubular string bore may be filled with fluid from the annulus simply by providing an opening at a lower end of the tubular string bore, it is often desirable to maintain a degree of control over fluid flow between the annulus and the tubular string bore. Such control may be advantageous, for example, to pressure test the tubular string periodically as it is being run in the well. However, if the tubular string is open-ended or is otherwise open to fluid communication with the annulus, it may be difficult or uneconomical to periodically close off the opening so that a pressure test may be performed, and then reopen the tubular string so that it may continue to fill while it is lowered further in the well. Additionally, when other items of equipment are pressure tested, such as after setting a packer, it may be advantageous to permit fluid flow through the opening in the tubular string. Furthermore, after the tubular string has been installed and various subsequent operations (e.g., pressure testing) concluded, it is sometimes advantageous to prevent or restrict fluid flow through the tubular string sidewall. For example, after a production tubing string has been installed it may be desirable to close off any opening through the tubing string sidewall, except at particular locations, so that hydrocarbons may be extracted.
Accordingly, there is a need for the ability to control fluid flow between the annulus and the interior tubular string bore. Preferably, control may be maintained whether the desired form is from the annulus to the tube string bore or vise versa.